Generally, in a fabricating method for a back-illuminated image sensor, sensing elements, a signal processing member, a dielectric layer, and metal wires are firstly finished on a front side of a silicon wafer. After that, a thinning process is performed on a back side of the silicon wafer to thin a thickness of the silicon wafer from several hundred micrometers to several micrometers, for example, from 750 micrometers to 3 micrometers. Then, optical members such as color filter and microlens are formed on a back surface of the thinned silicon wafer to introduce light beams from the back surface. In such a configuration, the light beams wouldn't be blocked by the metal wires. However, it is very difficult to accurately control the thinning process such that the thinned wafer after thinned several hundred micrometers has good cross-wafer uniformity and wafer-to-wafer uniformity. If the cross-wafer is over-thinned or unevenly thinned, the sensors on the front surface would be damaged or reduce the performance of the optical members on the back surface of the silicon wafer, and also the wafer-to-wafer thickness uniformity would affect the quality of the image sensors.
Therefore, how to solve the above problems and improve the yield rate and the performance of back-illuminated image sensors is an objective of the present invention.